1. Field of Invention
The present invention relates to a surface-treated mold, and a method of producing the surface-treated mold. More particularly, the present invention is directed to a mold with surfaces covered by a carbon film.
2. Description of Related Art
A technique that uses a mold to produce products with the same shape and quality in a large quantity is known. Japanese Patent Application Publication No. 2008-105082 (JP-A-2008-105082) describes a technique by which a surface of a mold is covered with a carbon film so that the product after molding can be easily taken out of the mold. In this technique, a surface of a mold is covered with fibrous nanocarbons to improve the abrasion resistance, corrosion resistance, thermal conductivity, friction properties and mechanical strength of the surface. When this technique is applied to a casting mold, for example, sticking of a melt to the casting mold can be prevented so that the service life of the casting mold can be increased. In the technique that is disclosed in JP-A-2008-105082, fibrous nanocarbons are allowed to grow on a surface of a mold to enhance the adhesion between the carbon film and the mold surface. The anchor effect of the fibrous nanocarbons prevents the carbon film from separating from the mold surface.
For example, in the case of a casting mold, when the carbon film separates from the mold surface, it is necessary to form a carbon film on the mold surface again. To reduce the number of maintenance of the mold, it is necessary to enhance the adhesion between the carbon film and mold. In the technique described in JP-A-2008-105082, a nitride layer and/or a sulfurized layer are provided between the carbon film and mold surface to enhance the adhesion between the carbon film and mold. In the technique that described in JP-A-2008-105082, a sulfide gas such as hydrogen sulfide (H2S) or carbon disulfide (CS2) is used to provide a sulfurized layer. Because these sulfide gases are toxic, it is necessary to provide the production apparatus with sufficient safety measures when such a sulfide gas is used. Thus, a need exists for a technique by which the adhesion between a carbon film and a mold can be enhanced without using a sulfide gas.